Yeah, if you can keep the cement from absorbing humidity, that's ideal. We finished ours about 5 years ago and I now have a 250 gallon down there, but we are there all the time, especially in the winter. I would say finish the basement first before putting a semi-permanent tank down there.
What we did: glue some Polystyrene sheets (pink) 2" thick to the cement, then frame over that, then seal the rim joist above to keep the critters and outside air out. Ventilate with an ERV, run a dehumidifier/mini-split to temper the moisture/heat as it now is well sealed.
Even if you don't go to that length, try and do anything you would do later to the tank area ahead of time. For example we put down "click" engineered flooring under the tank. After a flood we had to rip all the flooring up, and take down the tank (spoiler, I got a bigger tank). The new tank sits on an epoxy coated floor which held up nicely after hurricane Ida dumped hundreds of gallons down there last week.